Conventionally, radio advertising commercials are recorded on four-track tape cartridges which are arranged in a rack in a radio station broadcast booth. Other sound programs are recorded and handled in a similar manner, such as station identifier messages, jingles, program lead-ins and fade-outs, background sounds, musical recordings, and the like. When a cartridge is to be played, a disk jockey finds the desired cartridge, manually removes it from the rack, inserts it into a tape cartridge player and starts the tape to play. If the cartridge is a recording of an advertisement, an entry is made on a log sheet which provides data for notifying the sponsor that the number of plays contracted for have occurred.
The process of playing such tape recorded messages must be monitored in case a malfunction should occur. The tapes are subject to wear which degrades the sound quality, breakage, and cartridge malfunctions. The tape cartridge player is also subject to wear, tape head magnetization, and mechanical malfunctions which require that it be serviced periodically to avoid breakdowns and diminished sound quality.
Magnetic tape has developed to be the most practical medium for recording audio signals using analog techniques. There are also a number of digital techniques for recording audio signals. Digital media for recording relatively long programs, such a musical albums, include laser read compact discs (CD's) which are currently widely available and digital audio tape (DAT) which is just beginning to enter the market at this time. One advantage of digital sound recording over analog methods is that there is virtually no degradation of sound quality in duplicating a digital sound signal since digital copying involves copying binary codes rather than complex waveforms. While compact discs and digital audio tape can provide high enough sound quality recordings for broadcast use, they would require manual selection and queuing procedures similar to conventional tape cartridges. Further, compact discs are not well suited to low production runs and on-the-spot production, such that recording commercial messages thereon would be prohibitively expensive and require a long turnaround time between production and airing.
A number of personal computers have capabilities for playing fairly sophisticated sound programs, including stereophonic signals. For the most part, such facilities are digitally controlled music and noise synthesizers in which digital codes are sequenced to sound processor circuits to generate musical tones with selected envelopes and other qualities. There is also circuitry for synthesizing "speech" from data, including text data. Current musical synthesizer instruments often incorporate so-called "samplers" which perform analog-to-digital conversions on sounds, including vocal and musical sounds and random noises, which can then be altered in pitch and other qualities for incorporation in musical performances. Finally, there are devices for digitizing and playing back speech sounds, such as voice mail systems for recording telephone message and the like. To date, there are no systems available for on-the-spot digitally recording analog audio signals in stereo and playing back the signal at broadcast quality standards in real time which are economically practical to individual radio stations.